Ultraviolet-light cured, glass-reinforced pipe (UV GRP) is no longer viewed as a new technology in the CIPP world. It is estimated that more than 75 million feet have been installed worldwide, in 50 countries over the last 10 years. Advancements and refinements in equipment and materials have driven the market increasingly to choose UV GRP over traditional steam or hot water cured felt, especially in larger diameter applications. The product design and installation process offer benefits that appeal to both infrastructure owners and lining contractors, making UV GRP the smartest choice for superior quality and reliability.
One major difference between UV GRP and traditional felt is the fabric used to manufacture the liner. UV GRP has significantly greater mechanical strength properties, which enable designs to be thinner while still delivering increased durability and less impact on flow as compared to traditional felt, especially in larger diameter applications, and applications involving heavy loads. Because traditional felt is an unreinforced fabric, its function is only to carry resin into position to be cured, contributing little to no structural benefit once installed. The mechanical strength of the liner is provided primarily by the cured resin. In traditional felt deigns, the flex modulus of the liner can range from 250,000 to 400,000 psi depending on the designed wall thickness and subsequently how much resin is carried into place. A UV GRP liner is different; the fabric is reinforced with fiberglass, which substantially increases the mechanical strength of the cured liner. With flex modulus ranging from 1,660,000 to 3,000,000 psi, UV GRP can often deliver five to10 times the strength of traditional felt liners, in addition to a thinner liner wall that minimizes flow impact.
For example, an ASTM 1216 compliant designed in felt resulted in a wall thickness of 12.5 mm with a flexural modulus of 250,000 psi. With the same design parameters, a UV GRP liner has a 5-mm thick wall thickness and a design strength of nearly 2,000,000 psi flexural modulus. This increase in mechanical properties accompanied by a 60 percent reduction in liner wall thickness is a major advantage, especially in situations where pipes are already carrying flow at a 50 to 80 percent design capacity.